1. Field of the Invention
The present invention relates to a variable section nozzle for a turbo-jet engine, for example of the type comprising a partial re-heat system of moderate output and the invention also relates to an aircraft comprising such equipment.
2. Description of the Prior Art
A very large number of different types of variable section nozzle, for turbo-jet engines, are already known. For turbo-jet engines which utilize a re-heat system at high output, nozzles are generally known of which the variability of the section is provided by means of multiple blades or flaps. Nozzles having a complex structure, comprising several hydraulic actuators for the actuation of the various blades, and possibly mechanical means for synchronising the blades have also been proposed. Heavy, costly and very bulky constructions are involved which, moreover, often give rise to imperfect reliability, and necessitate periodic costly inspections.
Multiple blade nozzles of this kind are as a result poorly suited for the equipment of turbo-jet engines which only comprise a partial re-heat system of moderate output, particularly for reasons of weight and bulk.
British Patent Specification No. 1 306 588 describes a nozzle for a turbo-jet engine, which comprises a ring, which is coaxially mounted at the jet pipe outlet so as to be able to pivot on rails having a partially spherical profile. Multiple blades each controlled by a hydraulic actuator, are pivotally mounted on this ring, and they co-operate so as to form, in any position, a continuous wall of a nozzle of variable section. This construction has in practice all the disadvantages of multiple blade nozzles hereinbefore referred to.
French Patent Specification No. 1 497 418 describes a conical, variable-section, convergent-divergent nozzle, of the needle type. It comprises an inner bi-conical body, of which in particular the divergent part is formed by a folded thin metallic sheet following a frusto-conical surface, with overlap of its end edges, this sheet being capable of being wound up and unwound so as to cause a variation in the dimensions of the frustrum of a cone formed thereby. It has a very complex structure, and probably of low reliability.